Referenzbereich

A Referenzbereich is the span of values a laboratory considers usual for a healthy comparison group, most often derived as the central 95 percent of that group. By construction, one healthy person in twenty falls outside it.

Ranges are not universal, because they depend on the analytical method, the device, the units and the reference population the laboratory used. That is why the same marker can carry different limits at two laboratories and why a value cannot simply be copied from one report to another.

The working rule for a pharmacy follows from that, because the Referenzbereich that applies is the one printed by the akkreditiertes Labor that ran the analysis. A pharmacy quoting a range from a textbook or a website is quoting the wrong range.

A useful order at the counter has four steps.

1. Say what the marker measures before anything else.
2. Place the value in the analysing laboratory's Referenzbereich.
3. State plainly whether the value is unauffällig or auffällig.
4. Route anything unclear or markedly outside the range to a physician.

Two limits belong in the same conversation, because a single value is not a diagnosis and a trend across several measurements usually says more than one number. A result close to a limit often reflects Präanalytik rather than physiology, for example a sample that was in transit too long or a person who was not nüchtern when they should have been.

A Point-of-Care-Test carries its own device specific range, which is another reason not to compare its result directly against a laboratory report.